I. Field of the Invention
The present invention pertains to a test plug for use in testing equipment in the telecommunications industry. More particularly, the present invention pertains to a test plug and test assembly for testing electrical connections in a telecommunications terminal assembly.
II. Description of the Prior Art
In the prior art, terminal members in the telecommunications industry are well known for distributing or cross-connecting incoming telecommunication lines. An example of such is shown in commonly assigned and copending U.S. patent application Ser. No. 740,804 (now abandoned) which was filed on June 3, 1985 in the name of Loren A. Singer. The Singer application describes a U-shaped mounting bracket with individual terminals mounted on opposing tabs. The terminal is a block having two parallel opposing rows of wire connectors accessible through slots and apertures formed in the block. Shown best in FIGS. 4 and 5 of the Singer application, the opposing wire connectors or wire terminals (shown at 46) are electrically connected by a female electrical connection in the form of spring finger connectors identified by the numeral 50 in the application. A second female connector shown at numeral 68 and having a second pair of opposing spring finger connectors (shown at 68a and 68d in FIG. 5 of Singer) are disposed on a side of the first female connectors opposite the wire connectors 46. The second female connector 68 is electrically connected to a grounding strip 64. With the apparatus of Singer, telephone equipment lines and cross-connect lines are installed by placing the wire conductors within the split cylinder connectors 46.
As mentioned in the Singer application, telecommunication terminals are occasionally subjected to voltage or current surges which could damage equipment and present risk of harm to those in the vicinity of the equipment. As a result, such equipment is provided with an overload protection device. Shown at numeral 32 in the Singer patent application, the protection device includes a printed circuit board element 33 having its faces plated with a conductor pattern. The board element 33 is sized to be received within each of the first and second female connectors of the terminal. The conductor pattern on the circuit board element 33 includes conductor platings which would contact each of the spring finger connectors making up the female connectors. Opposite faces of the circuit board element 33 are electrically connected via plated-through holes such that the circuit board element 33 did not interrupt electrical connection between opposing spring finger connectors such as connectors 50 and 68a and 68a and 68d shown in FIG. 5 of the Singer patent application. The protection device includes a gas discharge element 140 which is electrically connected to the circuitry of the conductor platings. The gas discharge element together with the remainder of the circuitry of the overload protection device senses over-voltage conditions present on the conductors contacting the spring finger connectors 50 of the first female connector. In such an event, the circuitry of the protection device shunts the conductors to ground. In the Singer application, the end of the circuit board element 33 which is exposed includes electrical contact points on both faces of the circuit board which are in electrical contact with each of the spring finger connectors 50 of the first female connector.
As previously mentioned, telecommunication terminal blocks are provided with overload protectors for the safety of individuals as well as protection of the equipment. Another parameter for such equipment is the ability to occasionally test electrical connections between various wires entering the terminal. To this end, the art has developed test plugs which have contact elements which are inserted into the female connectors which are electrically connected to the wire terminals. The contact elements are in turn, electrically connected to a test lead which may transfer a signal from the female connectors to any one of a plurality of desired sources such as line mechanic's speaker phone or other connectors to provide cross-connects. An example of such a test plug is that manufactured by Krone GmbH of Berlin, Germany and described as Order No. 301,833 and 301,834 in the publication Krone "List of Equipment." As described in the Krone "List of Equipment", the test plugs of the prior art may have two or more contacts which are rigidly secured to a plug housing. The contacts are simply inserted into the female connectors of the terminal assemblies.
With prior art terminal assemblies provided with prior art overload protection devices, the protection device must be removed before the test plug can be inserted. As a result, during testing with such a plug, the equipment of the telecommunication terminal is not protected. This is particularly troublesome in terminal design where all of the connections within a particular terminal block are provided with an overload protector in the form of a magazine which covers the entire terminal block. An example of such a protector is shown as Order No. 301,811 in the aforesaid Krone "List of Equipment." This part is a magazine for a ten pair module such as module Order No. 301,221 shown in the publication. As a result, when a particular connection is being tested, not only is that particular connection deprived of its overload protector, but all other connections within the same block are deprived of an overload protector.
It would be desirable to provide a terminal assembly which simultaneously incorporates overload protection and means for permitting testing of electrical connections from time to time. It would also be desirable to provide such an assembly which is sufficiently versatile to permit testing of circuits with and without the presence of overload protectors. Finally, it would be desirable to provide such an assembly having assembly elements which are easy to use and easy to manufacture at low costs. However, such an assembly and elements have not been provided by the art.